Automatic and repertory dialing arrangements permit telephone system subscribers to access frequently called telephone numbers without time consuming and errorprone manual dialing. Such dialers find widespread use in the business environment where efficient utilization of telephone communication is economically important. Automatic and repertory dialing also permits handicapped persons who find it difficult or impossible to perform the manipulations required for manual dialing to use telephone communication without assistance.
While the number of manual operations needed to complete the dialing of a telephone number is significantly reduced in known repertory dialing systems, manual operations have not been eliminated. Some manipulation of the dialing apparatus is required for each call and additional manual processing is needed to insert or change the repertoire in the dialing device. It is desirable to design automatic and repertory dialers so that manual operations are completely eliminated. Speech recognition apparatus has been utilized to insert information into data processing equipment and to control mechanical devices without direct physical contact. Prior art speech recognizers, however, have been able to operate only with very restricted vocabularies.
U.S. Pat. No. 3,742,143 issued to M. Awipi on June 26, 1973 and assigned to the same assignee discloses a limited vocabulary speech recognition circuit for machine and telephone control in which an utterance is recognized as one of a limited set of vocabulary words. Detection of predetermined words may initiate telephone operations such as dialing. Awipi, however, requires each utterance to be recognized as one of the entire set of stored reference words. Any increase in the size of the stored reference words to incorporate an extensive list of names or additional commands substantially increases the difficulty of automatic recognition and reduces the accuracy of utterance recognition.
U.S. Pat. No. 4,164,025 issued to John J. Dubnowski and Aaron E. Rosenberg Aug. 7, 1979 and assigned to the same assignee discloses a spoken letter recognition arrangement designed to provide automatic directory assistance to subscribers over a telephone connection. This arrangement, however, requires spelled input in order to obtain a high degree of recognition accuracy. Other speech recognizers are similarly restricted in vocabulary for accurate recognition. The article "Computers that Talk and Listen: Man-Machine Communication by Voice" by J. L. Flanagan, Proceedings of the IEEE, Vol. 64, No. 4, April 1976, pp. 405-415 describes a recognition technique in which information is input to a computer via a man-machine dialog. A predetermined sequence of synthesized messages are generated. For each message, the recognition vocabulary is restricted to an answer ensemble appropriate to the synthesized message inquiry. These and other prior art recognizers are not adapted to automatic and repertory dialing wherein changing dialer vocabulary must conform to the user, an extended dialog is inefficient, and in which the error rate as well as the repeat dialing rate must be very low. For efficient operation, a spoken word recognizer is required to respond to any user utterance, to distinguish between speech meant to activate dialing and other speech and noise in factory, office, or home environments, and to accommodate a changing vocabulary of diverse names. It is an object of the invention to provide an improved automatic dialing arrangement which is controlled by spoken words.